Gain control circuit and receiving system

Abstract

Disclosed herein is a gain control circuit including: an amplifying section configured to amplify an input voltage in such a manner that amplitude of an output voltage at an output terminal is kept constant; an allowable voltage acquirer configured to acquire an allowable voltage of an apparatus connected to the output terminal; a voltage divider configured to divide the output voltage according to a ratio between a maximum voltage of the amplified input voltage and the allowable voltage; and an adjusting section configured to further amplify the amplified input voltage according to the ratio and supply a resulting voltage to the output terminal.

What is claimed is: 
     
       1. A gain control circuit comprising:
 an amplifying section configured to amplify an input voltage in such a manner that amplitude of an output voltage at an output terminal is kept constant; 
 an allowable voltage acquirer configured to acquire an allowable voltage of an apparatus connected to the output terminal; 
 a voltage divider configured to divide the output voltage according to a ratio between a maximum voltage of the amplified input voltage and the allowable voltage; and 
 an adjusting section configured to further amplify the amplified input voltage according to the ratio and supply a resulting voltage to the output terminal. 
 
     
     
       2. The gain control circuit according to  claim 1 , wherein the allowable voltage acquirer measures a voltage of the output terminal as the allowable voltage. 
     
     
       3. The gain control circuit according to  claim 1 , further comprising
 a table configured to retain the allowable voltage and the ratio in association with each other, 
 wherein the voltage divider reads out the ratio corresponding to the acquired allowable voltage from the table and divides the output voltage according to the ratio. 
 
     
     
       4. The gain control circuit according to  claim 3 , wherein
 the table further retains a signal format indicating whether or not the output voltage is a voltage of a differential output signal in association with the allowable voltage and the ratio, and 
 the voltage divider reads out the ratio corresponding to the signal format and the allowable voltage. 
 
     
     
       5. The gain control circuit according to  claim 1 , wherein the voltage divider divides the output voltage by insertion of a resistor. 
     
     
       6. The gain control circuit according to  claim 1 , wherein the adjusting section includes
 an adjustment amplifier that amplifies the amplified input voltage, and 
 a gain adjuster that adjusts a gain of the adjustment amplifier by changing a resistance value of a resistor connected to the adjustment amplifier according to the ratio. 
 
     
     
       7. A receiving device comprising:
 an amplifying section configured to amplify an input voltage in such a manner that amplitude of an output voltage at an output terminal is kept constant; 
 an allowable voltage acquirer configured to acquire an allowable voltage of an apparatus connected to the output terminal; 
 a voltage divider configured to divide the output voltage according to a ratio between a maximum voltage of the amplified input voltage and the allowable voltage; and 
 an adjusting section configured to further amplify the amplified input voltage according to the ratio and supply a resulting voltage to the output terminal. 
 
     
     
       8. A receiving system comprising:
 a gain control circuit configured to include
 an amplifying section that amplifies an input voltage on which a received signal is superimposed in such a manner that amplitude of an output voltage at an output terminal is kept constant in response to input of the input voltage, 
 an allowable voltage acquirer that acquires an allowable voltage of an apparatus connected to the output terminal, 
 a voltage divider that divides the output voltage according to a ratio between a maximum voltage of the amplified input voltage and the allowable voltage, and 
 an adjusting section that further amplifies the amplified input voltage according to the ratio and supplies a resulting voltage to the output terminal; and 
 
 a signal processing device configured to process the received signal superimposed on the output voltage.